Feline Claws

Did you know that the feline claw is not really retractable? It is a common mistake to refer to feline claws this way, as it gives a false impression of the way they really work. It is when a cat is relaxed that the claw is retracted, or sheathed. When the cat voluntarily tightens certain muscles the claws are unsheathed and ready for action. This makes the claws protractile, not retractile. This means they are capable of being lengthened or protruded upon demand. If the claws were retractile, the poor cat would have to keep its muscles tensed all day long. Cats have protractile claws for three main reasons, all related to survival. Climbing, hunting, and defense against predators are what nature intended in the development of the feline claw.

Most cats have 18 digits; five on each forefoot (including the dewclaw) and four on each hind foot. Cats are digitigrades, meaning only the phalanges make contact with the ground when they walk. A cat’s claw grows out of the distal phalanx of each toe. The claw is make of keratin, a very strong protein. When the cat wants to or needs to protract the claw, the digital flexor tendon becomes taut, forcing the claw to unsheathe. The blood vessels and nerves that supply the cat’s claws are located in the quick, the pink stripe observable at the base of light colored claws. The muscle responsible for protraction of the claw is the deep digital flexor. It is innervated by the median or ulnar nerve. It originates from the medial epicondyle of the humerus and inserts at the palmar distal phalanges.

Another misconception about cats and their claws is that they “sharpen their claws”. The correct term is stropping and it is a natural and necessary behavior. When the cat appears to be scratching, it is actually removing the old, worn-out claw sheaths, which then reveal new pin-sharp claws underneath. The claw grows in layers and after a period of time the outer layer must be shed. Stropping only applies to the forelegs. Cats use their teeth on their hind legs to chew off the old outer casings. A second reason for stropping is to exercise and strengthen the muscles used for claw protraction. A third function of stropping is scent-marking. The cat has scent glands located under the front paws and when the paw is rubbed vigorously against fabric it releases the cat’s pheromones onto the fabric. Lastly, cats scratch objects to calm themselves down and ease anxiety.

Have you ever wondered why cats knead? Kneading is the motion cats make by rhythmically alternating their paws, pushing in and out against a blanket or lap. Some cats protract their claws during kneading and some even use all four paws. It is a common behavior and may be accompanied by purring. There are several theories to explain kneading. Cats start to knead as kittens when they are nursing to help stimulate the mother’s milk production. As adults, cats may continue because they forever associate the motion with the rewarding comfort of nursing. If your cat is kneading your lap while you’re petting him, he may simply be returning your affection. Also, the simple action of kneading can provide exercise and stretching for the muscles in the legs, back, shoulders, and paws. Lastly, this natural instinct may have been “passed on” to domestic cats from their wild ancestors, who used kneading to compress tall grass and leaves for sleeping or giving birth.

It should now be apparent that cats do not possess those sharp talons solely to destroy furniture. The unique function of protractile claws allows cats to climb, hunt, defend themselves, remove old claw sheaths, exercise, and mark their territory. By learning about the physical claw, reasons for scratching, and the impact the toes and claws have on mobility, we can understand the actions of felines and provide safe and proper scratching options.